A medical image diagnostic apparatus is an apparatus for acquiring an image expressing an internal portion of a subject. An X-ray computed tomography (CT) apparatus and an X-ray machine are known as the medical image diagnostic apparatus.
The X-ray CT apparatus is an apparatus for imaging the internal portion of the subject by scanning the subject with X-rays, collecting data, and processing the collected data by using a computer. Specifically, the X-ray CT apparatus exposes the subject to X-rays from different directions a plurality of times, detects the X-rays that have passed through the subject by using an X-ray detector, and collects a plurality of detection data pieces. The collected detection data pieces are A/D-converted by a data collecting unit and then transmitted to a data processing system. The data processing system forms projection data by subjecting the detection data to pre-processing or the like. Subsequently, the data processing system executes reconstruction processing based on the projection data to form tomographic image data.
As further reconstruction processing, the data processing system forms volume data based on a plurality of tomographic image data pieces. The volume data is a data set indicating a three-dimensional distribution of a CT value corresponding to a three-dimensional area of the subject. In a case of acquiring the volume data, a volume scan using a multi-row type X-ray detector is employed. Further, by repeatedly performing the volume scan, it is possible to acquire a plurality of volume data pieces different in time phase (4D scan).
The X-ray CT apparatus can perform multi planar reconstruction (MPR) display by rendering the volume data in an arbitrary direction. An MPR-displayed cross-sectional image (MPR image) is classified into an orthogonal three-axis image and an oblique image. The orthogonal three-axis image represents an axial image indicating an orthogonal cross-section to a body axis, a sagittal image indicating a cross-section obtained by vertically cutting the subject along the body axis, and a coronal image indicating a cross-section obtained by horizontally cutting the subject along the body axis. The oblique image is an image indicating a cross-section other than the orthogonal three-axis image. Further, the X-ray CT apparatus sets an arbitrary line of sight and renders the volume data, to thereby form a pseudo three-dimensional image obtained when the three-dimensional area of the subject is viewed from the arbitrary line of sight.
Further, the X-ray machine is an apparatus for imaging the internal portion of the subject by irradiating the subject with X-rays and detecting the X-rays that have passed therethrough by using a two-dimensional X-ray detector. A photography method using the X-ray machine is classified into normal photographing for obtaining a still image by single X-ray irradiation and fluoroscopy for obtaining the moving image by applying X-rays continuously or intermittently.